Where I am gives cause to use 700s on a fairly regular basis.
If it was the only class that I ever experienced I'd say that it was fine, comfortable, quick and reasonably spacious.
However, it isn't; I also have the option of using 350s which are superior in every respect (even the 2s), compared to the 700s they feel premium, a little smoother, better seats and vastly superior ambience with the only downside being that they deposit one in the dreary smorgasbord of Euston.
My family occasionally uses the 700s on the full length of the line to Brighton for the convenience and no other reason; in days of yore we would go IC to London, tube, then the excellent Southern 319 to the coast (no sniggering in the back please, no exaggeration there).