What's "tegra" and why should I avoid it?
No, you shouldn't avoid Tegra. Tegra is the name of Nvidia's CPU/GPU that most Android Tablets / Phones use. However there are 3 different versions of the Tegra; Tegra 1, Tegra 2 and Tegra 3. The latest "Next-gen" tablets / phones are using Tegra 3 (and Snapdragon / OMAP / Exynos).
That said if you get a tablet now then you really want to get a Tegra 3 powered tablet UNLESS you can get a Tegra 2 tablet for a steal and when I say steal I mean under $250. Heck there's several Tegra 3 tablets (7 inch) coming in the Q2/Q3 2012 that supposedly under $200.
TL;DR If you want the best on an Android tablet get Tegra 3. Tegra 2 is also fine but it's a bit long in the tooth.
wish someone told me this before i bought a xoom (at launch)
I'm still rocking my Xoom though it's heavily modded using roms and I knew there were going to be some cheap Tegra 3 tablets coming, in fact Acer has one releasing this month; Acer Iconia A700. At the Xoom's launch the Tegra 2 chipset was the latest and greatest.
Edit - Yah, The Nexus tablet is going to have a Nvidia Tegra chipset at $250.00, 7 inches only but that's a damned good price and a nice format.