This does seem pretty important and it seems sg.net is oblivious.
The talent agency they mention does not even exists anymore
It has merged with another company on April 27, 2009
Before 2009, Hollywood's largest talent agencies were known as the "big five". In 2009 two of the agencies, Endeavor (where Summer was before now) and the William Morris Agency, merged to form William Morris Endeavor (WME). The other members of the current "big four" are Creative Artists Agency (CAA), International Creative Management (ICM), and United Talent Agency (UTA).
Anyone know about her new agent, or who she also represents?
Stephanie Comer is one of the 104 staff members (mostly talent agents) of United Talent Agency (UTA). She was a film assistant before becoming a talent agent but seem to be relatively new to the job.
She also represents 50 artists included Nathan Fillion, Jerry O'Connell, Alessandra Torresani (Caprica) for the best known and a lot a under 25 young actors and actresses (not A-list). In comparison with her former talent agent's list, Summer is now on top of her agent's priority in my opinion.
Without any inside information, it is very hard to deduce if the talent agency move is good or bad for Summer's carrer.
Imho, the choices she made after TSCC were all bad, except "Deadly Honeymoon".
Next big media coverage for Summer will be the annouce of the winner for the FHM 100 sexiest women 2011 contest in two weeks.
Feel free to ask any further information on agents that could be provided by IMDb.