The Classic Alien is definite buy. A great minifigure and a minifigure to use for so many mocs.
The head is one of the main reasons to buy, a very, very popular style for heads in alien movies, which makes it a very good figure to have. The only downside is the fact it can break very easily.
A good design, but very boring. A back printing would be far, far better.
The white blaster piece is a very good piece, and is a useful colour. The green ray piece really isn't needed ,as a 1x1 stud would be far better.
I'd say it's a definite buy, if you don't have one yet, go on ebay or buy one from your local shop.