The Charity Hotel is simply great value for the price. The biggest feat is its amazing garden, which is perfect for hanging out all day, or even working home office in the nature (the WiFi doesn't reach all corners, though). The air here is also much cleaner than in the city centre.
The rooms are clean and spacious, African standard plus. The downstairs rooms are rather dark and there's some moisture hanging in the bathroom, so trying to negotiate an upstairs room is advisable, though.
The street the hotel is in looks a bit dodgy, but is generally safe to walk, also after dark. The restaurant of this hotel doesn't sell beer or any other alcohol, but there's a local unmarked pub just 50m to the left on the street.
Arusha city centre is about 25 minutes walk away, but if you don't like walking, you can hail a Rikshaw from the main road and haggle a reasonable price. If you let the hotel order a taxi for you, you'll probably end up paying too much for the drive.