Modern bible translations: half good
Mainstream modern bible translations do two things very well.
1) Textual Criticism - getting the original letters right
There is widespread concern about working out the letters of the original texts as accurately as possible. A large amount of scholarly effort has been put into performing exhaustive analyses of surviving manuscripts. Published critical editions tend to be reliable and comprehensive. Biblical prefaces will usually discuss what critical editions were used and whether the translation team contained any experts in the field who used their own judgments. Most importantly, it is extremely common for translations to have footnotes that alert the reader to textual variants.
Of course, the lack of surviving manuscripts from the first couple of centuries places an inherent limit on the accuracy scholars can achieve. Equally it might be argued that scholars have made various mistakes or that the early Christians corrupted the texts. However, overall, there is a lot of concern about getting this right, a lot of effort put into it, and the reader is alerted about these issues.
2) Readable English - getting the English editing right
There is widespread concern about producing the most readable English translations possible. A large amount of effort gets put into improving the readability of the English versions. Biblical prefaces will usually discuss the ways in which they have aimed to improve readability. The diverse range of English translations offer readers a full spectrum of formal to colloquial language.
Of course, all translations have some verses that are hard to read or where the grammar is bad. The pros and cons of literal versus paraphrase translations can be endlessly debated. But, overall, a lot of effort gets put into making translations easier to read, and the variety of different English translations cater to all tastes.
Coming soon: Modern bible translations: half bad