I'm looking to buy a new guitar and could use some advice.
I have been playing on a Fender Strat replica (richwood stallion) for about two years and I think it's time for something new..
At first I wanted to go for a Les Paul model, because I like to be able to play some jazz as well as rock and just to play on a different model,
but now I'm considering a semi acoustic arch-top, e.g. an Eastman T386.

I have seen that semi acoustic guitars are favored by jazz players, but I'm wondering, how's the playability for a currently average skilled guitar player?
I've read about their sustain and that I would need to keep on playing notes to keep the phrase going, but I haven't confirmed.

I really want to have the jazz sound, an easy rig and warm sound, but on the side I'd actually like to be able to play along with some rock as well.

What do you think?
First of all, you should definitely ask this at the electric guitar subforum. This is the wrong section.

Something like a ES335 style instrument (a semihollow with humbuckers) could be a nice compromise for both rock and jazz sounds, and that Eastman you mentioned fits that exactly. Jazz is usually played on a fat hollowbody, something closer to a guitar like this: http://www.themusiczoo.com/images/2-15-13/17834_L5_Iced_Tea_SB_683561_1.jpg but these kind of hollowbodies might not work well with distortion tones.

However, I'm sure that a Les Paul would work just fine. The neck humbucky should give you nice, warm clean tones for your basic jazz needs. As far as playability goes, a guitar like the Eastman shouldn't be any more difficult to play than an LP.

Keep in mind that you also need a good amp in order to play such a wide variety of styles. As long as you have a dual humbucker guitar you shouldn't run into any problems if you just have a good amp.
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I agree with all that - amp, semi-hollows and hollows - and Eastman have a good reputation.

Ibanez make a range of semi-hollows and hollows, and the ones I have tried have had good neck profiles.

The only reservation I have is using covered humbuckers for rock. especially in a semi-hollow or hollow. I would be going for uncovered vintage style, possibly with series/single/parallel switching added - I have that on my 335 knockoff.
Semi-hollows are very popular with jazz players. I have an Ibanez myself and it's very nice. Set it up with flatwound strings as I play fingerstyle.

But... Jazz artists have used most everything you can think of. The big hollowbodys like the classic Gibson 175 are pretty much the standard for the more traditional players, but the semi-hollow has less tendency to feed back at higher volumes and usually has a bit more tonal color available.
More than a few solidbodies around... Ted Greene normally played a tele, for instance.

Considering how much control you have over the sound by your choice of amp and effects.... You can get a decent tone out of most anything.

The traditional jazz sound is "dry"....Tone controls rolled off on the guitar, amp settings rather neutral, maybe just a touch of reverb. But no one is holding a gun to your head. More rock-influenced players like Abercrombie and Chuquico and others feel free to add such effects as they like.
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More than a few solidbodies around... Ted Greene normally played a tele, for instance.

Plenty of all time jazz greats have played teles, like Jimmy Bryant and Danny Gatton.
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Thanks all, some great tips! I think I'll go for an Eastman T386, I have heard some interesting tones from that guitar.
My bad about the subforum by the way, I'm new here.