I think part of the problem with the Transform is that it only has 256kB of RAM, but the bigger issue (I think) is that (according to Engadget) Samsung didn't include an OpenGL graphics driver which would take advantage of the built-in graphics hardware. Samsung may implement a graphics driver in the Froyo release (but they never promised a graphics driver).
I ended up swapping my (800MHz-CPU/256MB-RAM) Transform for an LG Optimus S (600MHz/512MB) under the 30-day exchange window because the Optimus was so much faster than the Transform in download speeds and general usage. (LG implemented a graphics driver on the Optimus.) I don't care much about games, but the Optimus runs Angry Birds just fine, whereas the stock (2.1) Transform essentially couldn't run Angry Birds at all.
Neither the Transform nor the Optimus has a very powerful GPU, so they'll never be great gaming phones. And both use an ARMv6 CPU so neither will ever run modern Flash games, unless Adobe makes a big roadmap change that I don't foresee.