Hi Ive been thinking bout buying a 7 string-I'm still a little unsure if its the right thing to do so wondered if someone could tell me why I should and why I shouldnt buy one and perhaps which 7 string guitars would be a good buy-I have a budget of about £650 or $1350 (US).
No real reason not to buy
Reason to buy:
Extended range. i.e. you can do really heavy riffage yet still have the normal strings to solo on etc..
You'll be cool as a ****

Look at this page for some really nice 7s in every price range.

Schecters are good value for money, but the ibanezs rule.
I've developed a complex where everytime I hear a Lamb of God song, I burst out laughing

My 7 String V build
My Main Guitars:
Kramer Striker FR-2027SM 7 String
BC Rich Afterburner Warlock
Washburn Xb100 Bass
My Effect(s)/Misc:
Digitech RP350
Try a 7 string out and see if you like it? Honestly, the only disadvantage of a 7 string guitar is that you can't do chords made for 6 strings where you use your thumb on the low E. Also, if you have small hands, a 7 string is going to be quite uncomfortable. Find a guitar store that has one and try one out, see if you think you can handle it. As for the guitar, Ibanez RG7321 is a good buy unless you want a tremolo system - but I'm sure there's plenty of other good, cheap 7 strings as well.
I'm a communist. Really.