To be honest, I'm not sure. I've finished it right now (the Lambda Complex broke my poor gamer heart, since I wasn't able to save the guard that helped me.. as for Xen, it was every bit the mess they described me, those damn jump puzzles...), and I can understand why it was revolutionary at the time, and though it hasn't aged perfectly, it was still great fun to play and had some genuinely brilliant pieces of level design.
Right now, I'll either start with HL2 + episodes or being a Gothic 2 playthrough.
I'll think about it a bit.