"House Tremere would like to rule the world. This attitude alienates many of thier sodales." - True Liniages, pg. 116, Reverence for Order
I don't personally have a problem with Tremere, but thier constant readiness for war and desire to accmulate political and economical power (TL, pg 116, Military Ethos) can be intimidating. It reminds me of arms races, except who are they racing against? Tremere tried to take over the Order once, and conspratoralists could say they took out Diedne to increase thier own power.
"House Tremere dominates the Transylvania Tribunal absolutely. ...Another 20 magi and redcaps live in Transylvania as guests of the House. These are usually specialists, paid to create items and preform research." - TL, pg. 116, Extent
This knowledge doesn't give me a warm fuzzy.
On a side note on the comparison of Tremere and Mercere:
"A younger [Tremere] magus generally loses a season per year to the work of the House, less if he completes his duties early." -TL, pg 118, The Role of Young Magi
In the end, a Tremere magus would only go to a multi-house spring covenant if he was ordered to by his house. Makes me wonder as a PC of the covenant; why are the Tremere interested in this covenant? And there should be a reason, if only known by the SG. Tremere characters can also be removed from the covenant, if the House so wishes. Personally, I'm sitting on the fence for now about Tremere.