It's not bad at all, it just suffers from it's budget.

I watched this film twice already, as well as parts 1, 2 and 3.
I must say, while 1 still ranks as the best (And quite a good movie in it's own right, for what it is), whereas 2 and especially 3 i remain rather fuzzy about (2 is good, yet i was always disappointed by it, more so because i GREATLY anticipated it, while 3 is nothing special and it's too complicated for how uninteresting it is), this one is actually a very worhty follow up.
This movie has is a return to roots of sorts, taking back the simplicity of part 1, yet adding a new angle in a couple things (I liked the idea of the 3rd Sil specimen being used ilegally by a "rogue" scientist doing clones for financial goods), and Miranda is not only hot as hell, but also a bit of a role reversal from the original Sil, seeing as she has a predator inside which she can't control, but is not aware, and doesn't want to hurt anyone. (In a way i like that innocence in the Species female leads, even when Sil was a killer, you simply couldn't hate her, and felt bad for her at times too).
Still, i think this film was killed, in a way, by it's production. It is an interesting story, but it is hurt badly by it's low budget. I have no doubt a budget AT LEAST like the original's could have allowed them to explore the plot more deeply, as well as get better effects (i was put off at times by the glaringly obvious CGI, especially with the tentacles and blood squirts), and some better actors (In all fairness, The uncle, the scientist dude and especially Miranda, are actually very good, but i wanted to KILL the old texan and even more so Azura, who might have been hot, but was painfully bad whenever she spoke and moved around).
I think that if it had not been treated like some DTV reject and been taken on seriously, it could have turned out VERY differently.