Springer spaniels are active, loyal, affectionate and biddable. 'Biddable' means ready and willing to follow commands, as you would hope and expect from a retriever. With lots of energy, some people can see this as excitable, but that is not my experience.
This level of activity can be very high in some springers - they love exercise and need to be moving about. Of course this may not suit all owners, and if that is the case then the dog will be unhappy.
There are some differences between the Welsh and English Springers (their genes diverged a few centuries ago); there are even slight differences between the show-dog and working lines of the English Springer.
Let's look at each in turn:
Welsh Springer Spaniel
The Welsh Springer Spaniel (Welshie) has the doey-eyed faithfulness of spaniels in general, and are very devoted to their families. They are high-spirited, good-natured and loyal companions. Though they are people-orientated they but can be a bit shy with strangers at first. However, they very rarely show any aggression, except perhaps in the company of other dogs of the same gender.
They mix well with children and other household pets, but can be boisterous so a rough and tumble with very young children is not to be encouraged (though I never had any problems with my 1, 2 and 4 year old daughters). They are family dogs and need company, so they are best treated as part of the family.
English Springer Spaniel
The typical English Springer Spaniel is extrovert by nature, friendly, eager to please, easy and quick to train, and ready to obey. Springers continue to mature until they are about 2 years old. Aggression and dominance are rare but can be a problem if not handled with care when young.
Generally, the English Springers are great companions and family dogs, well-behaved and quick to learn and respond. Some of the less well-bred dogs of this breed can be stubborn or timid. It is said that some even resort to nipping and growling so check a pup's parents before you buy, if you can (I have never experienced this). If you are considering a rescue dog then you should check the dog's behaviour carefully, though this is not always easy. Bad behaviour is the exception, and I never observed it in my dogs (I've kept both English and Welsh Springers), but some people do report such problems.
The show-dog line of the English Springer appears to be less excitable and more placid than the working strain - but that is what you would expect after a hundred years of diverging bloodlines. Excitable show-dogs are not easy to handle in a show ring, and you certainly don't want a lazy dog when you are flushing game and retrieving.
Fun Loving
The other aspect common to both breeds is their love of fun. This is really good in a family environment, and their love of play is great for children. Do avoid games like tug of war with very young children for reasons mentioned earlier.
Guard Dogs
They are not the best guard dogs, but their shyness with strangers does mean that they will raise the alarm; in the last analysis their loyalty also means that they will defend the family.
Summary
In summary then their temperament makes them great family dogs, but they do need lots of exercise. They are happiest when not left alone all day, and with some garden or yard space to move around in. Highly active and fun loving, yes, but excitable, no.