I love it! I'd still like the option for a mode without a timer though - maybe reduce sell prices by 80% while it's active, but give us the option. At later levels the challenge is to get to the point total without running out of letters anyway.
Another possible mode could enable backwards spelling - so if you start dragging right-to-left or bottom-to-top, the letter order is reversed, giving more freedom and possibilities to find words - for example if you have "STNAP", dragging from the P to the S will count as "PANTS".
A small thing that annoyed me is that when you make a word, you can't start dragging the next one while the animation and scoring is going on, you have to wait, and when it ends, if your mouse button is down, it starts the selection immediately, which has screwed me over a couple of times by making a shorter word than I wanted to, because I started dragging earlier.
Also a few words without vowels like "TV", "UV" aren't in the dictionary, and I think they should. Once you run out of vowels, it gets tough.
And the museum slots are very expensive. Either make their price fixed (non-increasing), or lower it drastically, so you can at least get a good amount of slots early. Currently it is too grindy.
Here is my best run so far:
