Sound — 10
I used to use a Night Train and the Flexi-50 is a huge step up, in terms of sound and price. The Flexi-50 is an incredibly versatile amp, with great sounding cleans (which was lacking in all my previous 15w amps) and a great open-sounding overdrive. It must be noted that the volume must be high enough for the amp to sound more open. A lower volume will just make it sound as if the distortion is coming from a pedal. For flexibility's sake, I usually leave the amp at a clean-ish setting pretty near breakup (with the gain boost turned on, with gain and tone controls at around 12 o'clock). I'm using a Timmy as a boost, and I'm getting an EP booster and Black Arts Toneworks Pharaoh fuzz pretty soon. On higher gain settings, it produces a great British-sounding distortion, kinda like a uncompressed Plexi-ish tone with Vox-ish properties. Clean wise, it won't give you sparkling Fender cleans a la Deluxe Reverb, but the cleans do sound great, and I daresay slightly Fender-y and there is a lot of headroom before it starts breaking up. I do not have much experience with Vintage amps but I'd say this amp is like a open, uncompressed Marshall-sounding amp with traits borrowed from Vox and Fender amps. With regards to the noise, this amp is dead silent. I made sure to use a 3-pin plug when I use the amp. I'm not sure if the amp comes stock with a 2-pin plug, but regardless, with any amp, you should switch to a 3-pin plug to ensure that the amp is properly grounded. This does wonders to cure the noise issue. I use single-coil guitars (an American Vintage '62 Jaguar and a CIJ telecaster with Lollar pickups) and there is no humming issue, even at higher gain settings. I didn't put any effort into shielding the guitars, they just don't make any noise.
Overall Impression — 9
Overall, this amp is pretty much perfect for what I require at the moment. The only other thing I'd ask for is Fender cleans, but the existing cleans are good enough for me at the moment. I might experiment with 6L6/6V6 tubes in the distant future, and see if that gives me a better sounding clean. The existing EL84s are not disappointing me, however, and I'm getting an awesome sounding overdriven tone. This amp LOVES my Jaguar's neck pickup and the rhythm circuit (500k tone pot). It sounds too brittle with the bridge pickup (I never use it anyway) and the lead circuit (1meg pot). For most of my playing, I usually use the lead circuit with the 1meg pot, but I find myself really liking the thick sound I get with the rhythm circuit and neck pickup. I play mainly rock, and I dabble into bluesy material. This amp is great for rock players in general, and it will be perfect for classic rock players as well. I wouldn't recommend this amp to modern metal players, but with an overdrive pedal and the amount of gain on tap, I'm sure this amp would be able to produce great metal tones as well, though I haven't tried that (and I'm not really planning on doing so). The amp isn't an EXACT Marshall, despite the looks. However, it does give a unique take on the Marshall-y sound with borrowed properties from Vox and Fender amps.
Reliability & Durability — 9
I have not used this amp long enough to comment on this, but I have the cage version of the amp. For a more durability, there is an option to purchase the amp in the box version (Marshall style), or buy a box enclosure to replace the cage. The cage is easily removable to facilitate the swapping of tubes, tweaking, etc, and it shouldn't be much of a problem.
Features — 9
The "Flexi" in the name is not a reference to the "Plexi" sound, although the amp REALLY looks like a Marshall clone. The "Flexi" refers to the flexibility of the amp's tonal controls. One very distinct feature of this amp is its tweakability, giving users the option to replace the tubes with many options, leaving the user spoilt for choice. My Flexi-50 currently has Electro-Harmonix 12AX7s in the preamp section, and 2x Electro-Harmonix EL-84s in the power amp section. I'm looking to experiment with 6L6/6V6s in the distant future, but I'm pretty content with its current setup. Switchable 50w and 20w modes. I personally dislike the 20w sound and use the 50w setting all the time, the reason being the more compressed sound with the 20w setting. Volume knob, Hi/Lo switch (input), 3-band EQ with bright switch (I never use it), footswitchable boost switch (with gain and tone knobs), which I always leave on, regardless of whether I am playing clean or dirty, and a bypass-able master volume control, which is useful for late night playing. There is also a Cut control, which is similar to that of an AC30's. There is also an effects loop, which I do not use. You can use the amp with 2-4 and 4-16 ohm amps. I personally am using it with a Vox Heritage V112HTV 1x12 cab, loaded with a 12" Celestion Alnico Blue speaker. For now it is good enough and suits my needs, but I'm looking at 2x12 cabs as well. So far, the features suit my playing. I don't require any high gain distortion, and the cleans are great. The only thing it's missing is probably the THD HOT Plate, which I might be investing in, in the distant future. Then again, screw that, I love cranking this baby!