I thought he did a good job, he just didn't really have a lot to do. He hasn't acted professionally since the '80s, I believe, aside from his EE stints. I give him a lot of credit for that, and also for playing out a story of his husband dying of cancer when his real-life husband died of cancer. Admittedly I'm biased because Colin was one of my favorite characters.
The key for me was that last scene with Barry, which was just lovely. Initially I wasn't sure I wanted the characters to be back together because there was a very specific storyline about just why they were not meant to be (the age difference, Colin's fussiness, Barry's fear of being seen as gay, etc.) but hearing that they met up again through social media made sense. Colin being so eager to finally get to kiss him out in the open of Walford, after they had been so scared the last time they lived there together, and Barry's wonderment at it all - just absolutely lovely.
I don't mind seeing Lofty and Mary again, as they were such important characters for the early years. My main disappointment was no mention of Nigel. And yes, I didn't really love the part with everyone speaking, or Denise bringing up the Queen, although I could forgive as I'm sure it was hard to write.