Love this film. Jeff Goldblum is fantastic in it, even when he's unrecognisable under all the prosthetics, he still portrays the character so well and makes you feel for the 'monster' that he's become. Geena Davis is great too, I agree with Ammi that it probably wasn't the wisest thing her going back with him that first night, and I don't understand why he would have shown her his invention either with her being a journalist and him not wanting it to be written about, that's probably the only plot hole (besides the fact that it involves teleportation and a human morphing into a giant fly but y'know what I mean

)
The gruesome scenes are really gruesome but it's gore that has a place, rather than being just for the sake of it, and it's weird that a film can make you think "oh so that's what it'd be like if a person turned into a fly"

and for it to still not come off as silly or unnecessarily gross. It's testament to how well made it is, and how it could have failed horribly with different production/writing/performances. The final scene is heartbreaking, just a really emotional and powerful climax.
I give it 9/10. I can't fault it really, the only reason it doesn't get 10 is because, well, it isn't Muriel's Wedding... so
And a fun movie fact!: The phrase
'Be afraid, be very afraid' actually originated in this movie.
(Also, I would have loved a sequel that explored the scientific ramifications of his invention rather than the one we got. Like would the device had been refined and led to the fusion of other human/animal hybrids etc... for military purposes perhaps?

I'm just thinking out loud now but that would make for a great movie

)