I also rarely ever ask for an upgrade at check-in but in the last few years I have experienced it all: upgrades to suites or larger/nicer rooms. Sometime you get a room in the same category as booked but in a nicer/quieter part of the hotel. Many times I also get a room on the executive floor* (where you might have some extra perks such as free minibar) and just last week I was offered one of the first freshly renovated rooms at the Renaissance in Brussels.

* Of course as a gold/plat you will always receive access to the executive lounge, at least I was never denied access.