As I only own my TG55 for a couple of weeks (and do not own many other synths :) my opinion may not be the most objective one there is, but anyway: I like the sound of the machine, especially with some of the analog-type filtered patches I downloaded from the 'net (via the sy-links-page). The programming of sounds is a trifle complicated, because you usually have to click yourself through a whole lot of display pages before you find the right one... All in all (especially considering the low "used" price of about $300/DM450) I find the TG55 a good choice to start with. (Provided, of course, you already own at least one MIDI-keyboard ;-)
Comments About the Sounds:
I like em!
(Thanks to Lothar Bittner for this info.)
and JNR for the pic