I finished LEGO Harry Potter: Years 1-4 last week. To put it simply, I'm not impressed at all. First off, it doesn't allow me to actively save the game whenever I want to; it only autosaves whenever I accomplish something like complete a level or collect a bonus item, so that really restricts where I could find a good stopping point for the day. Also, in order to obtain all the character abilities I would need to complete the game, even with the help of a guide, I still had to really figure out where I could unlock such characters. As a result, while in other Lego games you could play each and every level a minimum of twice (once in story mode and once in freeplay mode), in this one I had to play some levels three times just to unlock the characters I'd need to access other areas. Switching between characters is also ridiculously difficult, so if you don't enter certain rooms with the right characters already selected, then you're pretty much going to end up trapped in there with no way out. And don't even get me started on how frequently this game crashed on me. Although I'm pleased to say that I did indeed successfully reach 100% game completion, the fact that there are certain points where it had a potential to become technically impossible to do so is just unacceptable. I would even go so far as to say that it was thanks to my OCD that I was able to make sure I could be very careful to avoid the issues that might've made the game impossible to complete. It took me more than 50 hours to complete the game, so if anything had happened at a later point that would've forced me to restart from the very beginning, well that would've been just absolutely infuriating, so I'm really glad it didn't happen to me (this time, at least). Needless to say, this is one Lego game that I won't be interested in ever playing again.
Next on my list of Lego games to play; LEGO Harry Potter - Years 5-7.
Since this is the other Harry Potter Lego game, I'm anticipating that it will also be not that great. I started playing it today and first impressions are that maybe a few issues from the previous game may have actually been dealt with for this later game. Of course, the only way I'll ever know for sure is to simply play through the whole thing and see for myself what it's really like.